United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-78-112
June 1978
Research and Development
Rapping
Reentrainment in a
Near Full Scale Pilot
Electrostatic
Precipitator
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect the
views and policies of the Government, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161. .
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EPA-600/7-78-112
June 1978
Rapping Reentrainment
in a Near Full Scale Pilot
Electrostatic Precipitator
by
Grady B. Nichols
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
Contract No. 68-02-1875
ROAPNo. 21ADL-027
Program Element No. 1AB012
EPA Project Officer: Leslie E. Sparks
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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DISCLAIMER
This report has been reviewed by the Industrial Environ-
mental Research Laboratory, U. S. Environmental Protection
Agency, and approved for publication. ; Approval does not signify
that the .contents necessarily reflect the views"and policies of
the U. S. Environmental Protection Agency, nor does mention of
trade names or ,• commercial products constitute endorsement or
recommendation "for-use.
-11-
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ABSTRACT
This report summarizes the results of an initial study to
define the reentrainment characteristics of fly ash being removed
from the collection electrodes of an electrostatic precipitator
by rapping forces. The details of the study are presented in
EPA-600/2-76-140, one of the Environmental Protection Technology
Series of Documents entitled "Rapping Reentrainment in a Nearly
Full-Scale Pilot Electrostatic Precipitator", May 1976. This
study was conducted at the Rosemont Laboratory of FluiDyne
Engineering in Minneapolis, Minnesota under the sponsorship of
the Industrial Environmantal Research Laboratory of the U. S.
Environmental Protection Agency at Research Triangle Park, N. C.
-111-
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CONTENTS
Disclaimer ii
Abstract iii
Figures and Table v
1. Introduction 1
2. Test Program 3
3. Computer Model Modification 11
4. Recommended Research 12
IV
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FIGURES AND TABLE
Number
Paqe
Figure 1
Figure 2
Figure 3
FluiDyne test facility.
Various views of FluiDyne pilot
precipitator
Block diagram of experimental layout for
rapping reentrainment study
Table I
FluiDyne Test Program 4-5
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SECTION I
INTRODUCTION
This document constitutes the final report under Contract
68-02-1875. The technical results of the study were published in
Report E.P.A. 600/2-76-140, "Rapping Reentrainment in a Nearly
Full-Scale Pilot Electrostatic Precipitator." This report sum-
marizes the project including a discussion of the inclusion of rap-
ping reentrainment in the E.P.A. electrostatic precipitator model.
The study included a preliminary laboratory investigation to eval-
uate the measurement techniques; a preliminary field study at
the FluiDyne Engineering pilot precipitator to evaluate the pre-
cipitator; a detailed field study to provide the rapping reen-
trainment data with analyses and finally, inclusion of rapping re-
entrainment data into the EPA-SRI electrostatic precipitator com-
puter systems model.
The overall objective of this research program was to ob-
tain the data necessary to provide a method for representing rap-
ping reentrainment in the computer systems model. The fundamental
processes in an electrostatic precipitator, including charging,
particle transport and collection can be mathematically modeled
from first principles. This, however, does not apply to reentrain-
ment. The quantity and particle size distribution of the reentrain-
ed material must be determined in order to include these data in
the computer system model.
This report discusses the results of an experimental investi-
gation of rapping reentrainment using a nearly full-scale pilot
precipitator at FluiDyne Engineering Corporation's Rosemont Labora-
tory. The work had three main objectives: (1) a study of the basic
mechanics of removal of dry dust by rapping and the variations in
the removal mechanisms with changes in dust properties, (2) quanti-
fication of rapping reentrainment in terms of the percentage of the
total losses, and of the particle size distribution of the reentrain-
ed dust, and (3) modification of the E.P.A. - S.R.I, computer sys-
tems model to include losses due to rapping reentrainment into the
computation process.
The laboratory study carried out under Task I utilized the
E.P.A. pilot scale electrostatic precipitator located at S.R.I, to
evaluate the proposed measurement techniques for use on the FluiDyne
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facility. The collection electrodes in the pilot E.S.P. were
instrumented with an accelerometer system that had been calibrated
by the use of an electromagnetic shaker facility.
Experiments were conducted to evaluate the ability of the in-
strumentation to discern the presence of rapping puffs. Individual
impactors were operated during the particulate collecting period
and during the rapping period to check their operation. Movies of
the behavior of the dust layer were made during rapping to evaluate
that system. The experiments showed that the equipment could be
used to make measurements to identify the contribution of rapping
puffs to the overall emission in the FluiDyne pilot precipitator
facility.
Tasks II and III are covered in detail in Report No. E.P.A. -
600/2-76-140, Rapping Reentrainment in a nearly full scale Pilot
Electrostatic Precipitator, dated May, 1976. These two tasks are
summarized in this report.
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SECTION II
TEST PROGRAM
A ten day test program was conducted at the FluiDyne test site
as indicated in Table I. A schematic of the Fluidyne facility is
shown in Figures 1 and 2. Figure 3 shows a block diagram of the
test program.
The experimental program included a fundamental study of the
mechanics of removal of dry dust by rapping and the quantification
of rapping reentrainment in terms of the percentage of total emis-
sions and particle size distribution of the reentrained dust. The
percentage of dust removed from the plates depended on the mass per
unit area of dust collected on the plates as predicted by theory.
The build-up of a residual dust layer was observed. A residual dust
layer developed that could not be removed with the available rap-
ping intensities (up to 20 G's).
The contribution of rapping reentrainment to total emissions
ranged from 53% to 18%, depending on rapping conditions. These
percentages corresponded to 5.4% and 2.7%, respectively, of the
dust collected on the plates being emitted during plate rapping.
A significant decrease in total rapping emissions was obtained by
increasing the time interval between raps. This decrease was re-
lated to the resulting larger mass per unit area collected on the
plates before rapping.
Particle size distribution measurements showed that the mass
median diameter of the particles emitted during the raps increased
with increased time between raps. As expected, this produced lower
overall emissions. The increase in the size of the particles emit-
ted during rapping was ascribed to an increase in the agglomeration
of the particulate removed from the precipitator plates with the re-
spective increase in the mass per unit area collected on the plates
(thicker dust layers) before the plates were rapped. A major por-
tion of the reentrained material resulted from hopper "boil-up".
A small portion of the dust would pass directly through the precipi-
tator in a short burst at the velocity of the gas passing through
the unit, while the remaining portion of the material was observed
to fall into the hoppers, to rebound, and finally to escape slowly
over the baffles and out of the precipitator. This produced a
significant vertical concentration gradient in the dust emitted
from the precipitator due to rapping reentrainment.
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TABLE I
FLUIDYNE TEST PROGRAM
June 16
June 17
June 18
June 19
June 20
June 23
Unloaded and set up equipment.
Clean plate rapping accelerations, equipment
checked.
Conditioned impactor substrates, tested for
weight gains, clean plate V-I characteristics,
gas velocity at sampling locations, adjusted
for desired flow, measured gas velocities at
entrance and exit planes of the precipitator,
tested dust feed system, tested real time
sampling system.
Measured inlet particle size distribution,
inlet mass loading, and tested load cells.
Checked mass trains and impactors to detect
rapping puffs. Measured dust resistivity and
adjusted for 1010 ft-cm.
Ran efficiency test with following conditions:
Dust feed
Current density - 23 nA/cm2
Gas velocity between plates - ^0.91 m/sec
Rapper intensity - 80% of maximum
Rapper interval - 30 minutes inlet
- 60 minutes outlet
Start intensive test program.
All variables except rapping intensity and time
interval between raps were held constant. The
quantity of dust reentrained and the variables
affecting reentrainment were measured.
Test 1 150 minutes between raps, rapping in-
tensity 100% of maximum, 1 rap
Test 2 120 minutes between raps, rapping in-
tensity 100% of maximum, 1 rap
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TABLE I
FLUIDYNE TEST PROGRAM
(continued)
June 24
June 25
June 26
June 2 7
Test 3 12 minutes between raps, rapping in-
tensity 80% of maximum, 6 raps
Test 4 32 minutes between raps, rapping in-
tensity 80% of maximum, 3 raps
Test 5 12 minutes between raps, rapping in-
tensity 100% of maximum, 6 raps
Test 6 32 minutes between raps, rapping in-
tensity 100% of maximum, 3 raps
Test 7 52 minutes between raps, rapping in-
tensity 80% of maximum, 3 raps
Test 8 52 minutes between raps, rapping in-
tensity 100% of maximum, 2 raps (rain
and wind knocked out electrical power
and burners, test was terminated 15
minutes after second rap)
Test 9 Deleted due to internal electrical
short in the precipitator.
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CTi
NOMINAL 48 IN. WIDTH
FOR (5) PASSAGES
EXPANSION TO
TEST PRECIPITATOR
STEAM
TO MATCH
CONDITIONS
FLOW RATE TO
45,000 SCFM
TEMP-AMBIENT-40O°F
HUMIDITY TO 8%
ASH FROM H2S04 + HOT AIR (650°F)
CLIENT'S STATION
(FROM PRECIP. HOPPERS)
TO MATCH CLIENTS CONDITIONS
Figure 1. FluiDyne test facility
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TYPICAL FLOW
9 FT/SEC
300°F
35000ACFM
SCA5I.4
* 9 ACCELEROMETERS
ARE MOUNTED ON PLATE 4
NORTH
EAST
SECTION A-A
WEST
CHANNEL NO
PLATE ROW NUMBER
PLATE ROWS 1, 2, & 6 EXPANDED METAL
PLATES ROWS 3, 4. & 5 SOLID
PLATES 2-1 and 2-3 WERE
SHORTENED.5 METERS
Figure 2. Various views of FluiDyne pilot precipitator.
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ELECTRICAL
CHARACTERISTICS
RAPPING
VARIABLES
DUST LOAD
ON PLATES
PLATE ACCELERA-
TION
GAS ANALYSIS
SO3, SO2, H2O
TEMPERATURE
00
RESISTIVITY
MEASUREMENT
MASS LOADING
TIME INTEGRATED
PARTICLE SIZE
MEASUREMENTS
VELOCITY
DISTRIBUTION
TWO SETS AT 3 LOCATIONS: ONE TO MEASURE DURING
RAPS AND ONE TO MEASURE BETWEEN RAPS.
TWO SEPARATE UNITS: ONE TO LOOK AT LOWER HALF OF THE
PRECIPITATOR OUTLET AND ONE TO LOOK AT UPPER HALF OF
THE PRECIPITATOR OUTLET.
PRECIPITATOR
OBSCURATION
METER
TIME INTEGRATED
PARTICLE SIZE
MEASUREMENTS
MASS LOADING
UPPER HALF
CAMERA AND
LIGHTING
MASS LOADING
LOWER HALF
HOPPER
SAMPLES
•• REALTIME
PARTICLE SIZE
MEASUREMENTS
Figure 3. Block diagram of experimental layout for rapping
reentrainment study.
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The fractional collection efficiencies of the precipitator
excluding and including rapping reentrainment emissions were de-
termined and compared with theoretical values. Rapping reentrain-
ment increased the discrepancy between theory and measured frac-
tional collection efficiencies for particles larger than 5ym.
However, rapping reentrainment did not account for all of the dis-
crepancy. Reentrainment between raps and sneakage through the
nonelectrified regions of the precipitator were considered to con-
tribute to overall emissions.
The experiments provided data that suggested some problems in
detailed mathematical modelling of rapping reentrainment. It is
difficult to predict the quantity of dust removed from a plate by
an individual rap. The calculation of the recollection of the re-
entrained material is difficult for several reasons. The particle
size distribution of the reentrained particles can be changed sig-
nificantly by moderate changes in rapping variables and hopper boil-
up also contributes to the difficulty in modelling since much of
the reentrained material is introduced into nonelectrified regions
of the precipitator. However, the experiments supplied some infor-
mation that could be used to estimate the effects of rapping reen-
trainment on the size of a precipitator required for a given col-
lection efficiency.
Two simplified assumptions were used to estimate the signifi-
cance of rapping reentrainment. The first assumption was that a
fixed percentage of rapping emissions was emitted from a precipita-
tor independent of the size of the unit, while the second assump-
tion was that the same percentage of material was reentrained and
emitted from each section due to rapping. The recollection effi-
ciency for the reentrained material was assumed to be the same as
that for previously uncollected material for all sections. The
estimates based on the above showed that the increase in precipi-
tator size needed to recover the rapping emissions can range from
6% to greater than 80% of the original size of the unit for the
cases considered. Rapping reentrainment emissions computed on the
basis of the percentages obtained at FluiDyne account for a signifi-
cant portion of precipitator emissions.
Initially, four weeks of tests were planned for Tasks II and
III. At the conclusion of the test period described previously in
Table I, the status of the test results and the funding situation
was reviewed. It was determined that:
1. Additional funds would be required to conduct two
more weeks of tests.
2. The results of the tests to date provided suffi-
cient data for the pilot test facility.
Therefore additional pilot scale tests were cancelled.
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During the period of this research contract, the Electric
Power Research Institute had funded a study of Rapping Reentrain-
ment at a number of full scale installations. The Industrial En-
vironmental Research Laboratory of E.P.A. and the E.P.R.I. agreed
to cooperate on the rapping reentrainment study. The result of
the E.P.A. pilot study served as a guide for establishing the test
program for the E.P.R.I. field tests.
This field test program included rapping reentrainment measure-
ments at six installations described as follows:
- Two cold side units collecting fly ash from the com-
bustion of low sulfur Western coal.
Two cold side units collecting fly ash from the com-
bustion of high sulfur Eastern coal.
One hot side unit collecting fly ash from the com-
bustion of low sulfur Western coal.
One hot side unit collecting fly ash from the com-
bustion of low sulfur Eastern coal.
The results from these tests have been reported, in draft form,
to the E.P.R.I. in a document entitled "Electrostatic Precipitator
Rapping Reentrainment and Computer Model Studies", August 15, 1977.
A copy of this draft report was submitted to the Industrial En-
vironmental Research Laboratory, Environmental Protection Agency,
Research Triangle Park, North Carolina for review.
10
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SECTION III
COMPUTER MODEL MODIFICATION
Task IV of the E.P.A. contract was to include rapping reen-
trainment into the E.P.A. - S.R.I, electrostatic precipitator com-
puter systems model. The results of the measurement program con-
ducted at the above six full scale field installations have been
reviewed, analyzed and used to develop a calculation procedure for
approximating the magnitude of rapping reentrainment emissions as
follows:
1. The dust concentration removed from the flue gas by the
last field was estimated from the Deutsch equation and
the overall mass efficiencies obtained during the test
programs at each installation.
2. The overall mass emission (in mass/volume of flue gas)
attributable to rapping were graphed as a function of
the dust calculated to have been removed by the last
field for each of the six installations.
3. The rapping emissions were represented as a function
of the dust removal in the last field by a simple ex-
ponential expression, and the expression was programmed
into the computer model.
4. Data from the six installations were used to construct
an average apparent size distribution of a rapping puff.
This size distribution is then applied to the mass emis-
sions caused by rapping and calculated in step 3 above
to obtain a histogram of rapping emissions as a function
of particle size.
5. The size dependent rapping emissions are then added to
those calculated by the model to originate from the
steady-state, non-rapping precipitator process.
A draft report has been transmitted to I.E.R.L. that de-
scribes this expanded version of the computer systems model. This
updated a previous report No. E.P.A. - 650/2-75-037, "A Mathemati-
cal Model of Electrostatic Precipitation", dated April, 1975. This
new version of the model contains the currently available rapping
reentrainment computer program modifications as well as other modi-
fications developed under E.P.A. Contract 68-02-2114.
11
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SECTION IV
RECOMMENDED RESEARCH
The method utilized to represent size-dependent rapping loss-
es in the computer model described previously in this report is an
empirical one based on an average apparent size distribution of
particulate emissions attributable to rapping. The size distribu-
tion data were obtained from full-scale field tests. The total
mass emissions from rapping are also represented empirically. The
procedure used is based on a simple relationship between the mass
calculated to have been collected in the last field of the precipi-
tators and the rapping emissions measured during field tests. Al-
though this procedure represents a useful interim technique for
estimating rapping reentrainment in precipitators, it is desirable
to include rapping into the model in a more fundamental way for
modeling precipitator performance.
The ESP computer model program calculates particle collection
rates for representative particle sizes as a function of length
through the precipitator. This basic calculation procedure is
suitable for including a dynamic representation of reentrainment
resulting from a particular rapping system design. The particulate
reentrained as a result of rapper activation in a given field at a
given point in time may be thought of as a pulse in the particulate
concentration in the field under consideration. A technique to
model the reentrainment of dust from first principles should in-
clude consideration of the following problems:
1) What are the size distributions of the reentrained par-
ticulate from the various fields and what fraction of
the collected mass is reentrained?
2) To what extent is the particle charging process disrupted
by the sudden reintroduction of a significant particulate
concentration?
3) To what extent are the reentrained particle remixed with
the gas stream?
4) What collection mechanism can best represent the recapture
of reentrained particulate? Since a Deutsch-type mechanism
is valid only for smaller particles which follow the mo-
tion of the gas stream, we anticipate that the reentrained
12
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material (dominated by the larger agglomerate, >5 jam
diameter) will require a different mathematical ex-
pression to represent the trajectory.
5) Does the pulse of dust resulting from a rapper activa-
tion cause a momentary decrease in sub-tenth micron par-
ticulate emissions due to the sudden increase in poten-
tial surface area for agglomeration.
6) What relationships can be formulated to represent the
cumulative mass size distribution of the reentrained
material as a function of the following variables?
a) Rapping interval
b) Ash and gas composition, temperature, and size
distribution of collected dust, which determine
dust cohesive and adhesive properties.
c) Plate acceleration
d) Plate response
e) Mass loading of dust on plate
f) Plate geometry
g) Gas velocity
h) Electrical holding forces
It is apparent from the nature and the complexity of the re-
entrainment process that some degree of empiricism must be incor-
porated into a modeling approach. However, since the existing
mathematical model is able to simulate the collection process with
reasonable accuracy, a logical approach would be to use the exist-
ing program structure as a basis for calculating the recollection
of reentrained dust. Once this task is accomplished, it would be
possible to examine the effect of rapping frequency and certain
precipitator design parameters on overall collection as a function
of particle size for various assumed input cumulative mass distri-
butions resulting from electrode rapping. The complete modeling
of the reentrainment process must include the task described in
item 6 above, which essentially involves the prediction of the rap-
ping pulse in the various fields as a function of dust properties
and precipitator design and operating parameters. Thus, there are
two major subdivisions to the recommended approach for a more rig-
orous treatment of the reentrainment process: 1. Expanding the
computer program to obtain the capability to calculate time-depend-
ent emissions from the existing input data set (Electrical condi-
tions, SCA, precipitator geometry, size distribution, etc.) plus a
rapping interval -schedule for the various fields and an assumed
13
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cumulative mass distribution for the rapping pulse. 2. Prediction
of the rapping pulse distribution from dust properties and precipi-
tator design parameters.
In view of the above considerations, our suggestions for fol-
low-on work are as follows:
1) Expansion of computer program
a) Develop a flow chart of a computer program based on
the existing model, but with the capability of dy-
namically representing rapping programs with various
intervals for the different fields in the precipitator.
b) Develop appropriate mathematical relationships for
representing the dynamic behavior of reentrained
particulate in the precipitator. The objective is
to formulate a collection mechanism theory appro-
priate for reentrained dust.
c) Examine the data obtained previously with the ob-
jective of finding a procedure to represent the
sporadic large particle emissions not associated
with rapping.
d) Develop a FORTRAN program with items 1-3 included.
e) Use the expanded program with various assumed cum-
ulative mass rapping pulses and the rapping fre-
quencies of the rapping programs at the six test
sites. Compare computed results with time integrat-
ed measurements obtained with impactors.
2) Prediction of rapping pulse size distribution
a) Modify existing large particle real-time counting
system to allow for traversing of the duct system.
Develop procedures for calibrating the readout with
absolute value of in situ particle concentrations.
b) Design a test program to use the instrument at
several sites with the objective of relating the rap-
ping pulse (from various fields in the precipitator)
to dust properties and precipitator operating para-
meters. The test requirements could be less than is
normally required for control device evaluation be-
cause of the restricted data requirements.
14
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c) Correlate results and use in 1 above to expand model
capabilities.
The two major tasks described above could be conducted simul-
taneously or in series.
15
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TECHNICAL REPORT DATA
(Please read liatructions on the reverse before completing)
I REPORT NO.
EPA-600/7-78-112
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Rapping Reentrainment in a Near Full Scale Pilot
Electrostatic Precipitator
S. REPORT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Grady B. Nichols
8. PERFORMING ORGANIZATION REPORT NO.
SORI-EAS-78-019
3489-Final
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
2000 Ninth Avenue, South
Birmingham, Alabama 35205
1O. PROGRAM ELEMENT NO.
1AB012; ROAP 21ADL-027
11. CONTRACT/GRANT NO.
68-02-1875
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND
Final; 5/75-4/78
PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES jERL-RTP project officer is Leslie E. Sparks, Mail Drop 61,
919/541-2925. EPA-600/2-76-140 is an earlier related report.
16. ABSTRACT
gives results of a research program to identify the character-
istics of particulate matter reintroduced into a gas stream flowing through an elec-
trostatic precipitator (ESP) attributable to collection electrode rapping. The study
included both fundamental and experimental studies of dust layer behavior in a pilot-
scale ESP with collection electrodes of a size that approximates those in a full-scale
field unit. Results of the pilot study , together with those of a related study of full-
scale ESPs collecting flyash from coal-fired boilers, were used to modify the EPA
Computer Systems Model of an ESP to more nearly represent the actual behavior
of this class of particulate control device.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution Combustion
Dust Boilers
Electrostatic Precipitation
Entrainment Mathematical Modeling
Fly Ash
Coal
Air Pollution Control
Stationary Sources
Particulates
Rapping
Reentrainment
13B
11G
13H
07D
21B
21D
13A
12A
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report/
Unclassified
21. NO. OF PAGES
21
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
16
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